Refining mineral oil



2 Sheets-Sheet l Filed Jan. 3l, 1934 ATTORN EY May 19, 1936. M. H. TUT'rLE 2,041,303

REFINING MINERAL OIL Filed Jan. 31, 1934 2 sheets-sheet 2 ATTORNEY Patented May 19, 1936 PATENT OFFICE REFINING MINERAL OIL Malcolm H. Tuttle, New Rochelle, N. Y., assignor to Max B. Miller Co., Inc., New York, N. Y., a corporation of Delaware Application January 31, 1934, Serial No 709,097

11 Claims. (Cl. 196-13) This invention relates to refining mineral oils by means of solvents.

Mineral oils are composed mainly of mixtures of compounds of hydrogen and carbon, certain of which are particularly useful as lubricating oils, for instance for internal combustion engines. Others are not desired in lubricating oils but nd other uses. For convenience, the first type oil will be referred to as paraiiinic and the other type as naphthenic oil.

In my copending application Serial No. 623,483, filed July 20, 1932, there is described a highly advantageous process for separating a mineral oil into a lubricating oil fraction of superior quality, and another fraction containing the balance of the mineral oil. Such, process has especial advantages when applied to asphalt base or mixed base residuums resulting from the topping of crude oils to remove gasoline and/or kerosene, though it is also useful for treating other oils.

Now, in the refining of certain types of mineral oils advantages are to be derived by distilling off a relatively light lubricating oil fraction and separately rening such distillate fraction and the residual oil. While a distillate oil may be treated or rened by the process of the above mentioned application, it has now been found that superior results may be achieved if such oil be solvent extracted in the presence of a naphthenic fraction previously extracted from a mineral oil or preferably from a residual oil.

A feature of the present invention thus resides in'the employment of a naphthenic or tarry fraction of a mineral oil or a residuum to assist in the solvent extraction of a relatively light oil, such as an overhead distillate. ,4

Another feature resides in the provision of a novel and improved process for the eicient soln in providing an improved process for preparing lubricating cils having different -viscosities, so that they may be blended to produce oil of. various commercial viscosities, which oils shall have desired properties including a high viscosity inneed for excessive, costly apparatus.

Other features, objects and advantages will become apparent as the following detailed description of illustrative processes in accordance with the invention proceed, reference being had to the accompanying drawings, wherein:

Fig. 1 is a diagrammatic ilow sheet indicating one such process.

Fig. 2 is a diagrammatic flow sheet showing certain additional steps in accordance with the invention.

Referring toFig. 1, a crude or charge oil may first be topped in the usual manner to take of! gasoline, kerosene, and gas oil. A light oil fraction may then be distilled, for instance in a manner similar to present refinery practice, the end point temperature preferably being kept below that at which constituents desired as lubricants would be decomposed. 'Ihe residual oil may then be introduced to a solvent extraction apparatus 5 where it is intimately mixed with solvents which are selective for the paraiiinic oil and for the naphthenic oil, respectively.

Preferably, the paraiiinic and naphthenic solvents are counterfiowed and the preferable oil is introduced in the middle of the system under conditions such that the solvents are miscible to only a limited extent, so that the oil is separated into paraflinic and naphthenic fractions carried by the respective solvents.

In this manner it is possible to dissolve the en-` tire residual oil and at the same time to provide for eiiicientextraction fromeach fraction of constituents which belong in the other fraction. However, while such process is especially advantageous for reasons indicated and others, the.

present invention in its broader aspects is not limited to any particular type of extraction.

The solvents employed may be such as disclosed in my Patents No. 1,912,348 and No. 1,912,349 and in copending applications Serial No. 623,483, filed July 20, 1932-and Serial No. 688,271, filed September 6, 1933. For instance,

propane vor natural gas fractions liquefied by plished before or after the extraction), will be pressure, are useful as parafllnic solvents, while nitrobenzene and cresylic acid, alone or in mixture with pyridine phenol, furfural, or aniline are examples of useful naphthenic solvents. The selective parafinic and naphthenic solvents are preferably miscible to only a limited extent; under the temperature conditions prevailing during the extraction, so that a good separation may be secured. The amounts of solvents employed may vary but several volumes of ea'ch solvent per volume of oil are generally prefered for efficient extraction to avoid excessively long periods of extraction or slow rates of separation as Well as extremely intimate mixing of the solvents and oil to produce the desired contact between them.

In one manner ofconducting the extraction, the oil may be continuously introduced into the middle of a tower, the lighter solvent near the bottom, and the heavier solvent near the top. The immiscible solvents and dissolved constituents are withdrawn from top and bottom of the tower. When the paraiiinic solvent solution is lighter than the naphthenic solvent solution, the former will be withdrawn at the higher level, the latter at the lower level. The temperature in the extractor should preferably be maintained below the critical temperature at which the solvents are miscible, and where a normally gaseous parainic solvent is used the materials are maintained under adequate pressure to keep the solvent liquid. If desired, the extraction may be accomplished by batch treatment instead of continuously, preferably in countercurrent stages.

The parafinic oil fraction, including paraiinic solvent and some entrained naphthenic solvent and possibly some naphthenic oil, may then be passed to a solvent evaporator 6 where the paraflinic solvent is evaporated and recovered for reuse. Where some naphthenic solvent is entrained in the upper layer, this may be separately, fractionally distilled, and returned to storage for reuse. The parainic oil thus produced, after dewaxing (which may be accomfound to have excellent properties as a. lubricating oil. The process is especially advantageous for producing oils having a high viscosity index (i. e.

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a relatively small reduction in viscosity when heated from F. to 210 F.). For example, oils having a viscosity index of over 100 may be produced from residual oils in a simple and eilicient manner. Moreover, a higher yield of oil is obtained than has heretofore been possible with most crudes.

A rather remarkable feature of this solvent extraction process is that it is particularly suited to extracting relatively heavy or residual oils containing considerable or even high amounts of asphaltic type constituents, and excellent results have been achieved when operating on such oils. However, the process is less eilicient for light oil distillates,rfor instance of the character commonly taken overhead from Pennsylvanian or Appalachian crudes. It has now been found that improved results may be achieved by solvent extracting such a distillate, or similar light oil, in the presence of the naphthenic or tarry (asphaltic) fraction removed from a relatively heavy or residual oil.

While it would ordinarily be possible to solvent extract the whole crude in a single operation, it is highly desirable under certain circumstances to remove a light oil from the crude charging stock byv distillation, for one reason to obtain a light fraction useful for blending. For

another reason, it may be desirable to dewax, or remove wax from, the light oil by asomewhat diiferent procedure than is most suitable for dewaxing heavy oils. There are other advantagesto this practice, but suffice it to say that when a distillate is to be treated with a solvent or solvents, excellent results may be achieved by mingling a naphthenic layer from a relatively heavy oil with the light distillate either prior to introducing them into the extraction system or during the extraction operations. For instance, a naphthenic layer and solvent drawn off from the bottom of extractor 5. may be introduced into an extractor 5' at a point above the point where light oil is introduced, and paraiiinic and naphthenic solvents may be counterflowed as in the extractor 5. If in some instances suflicient naphf thenic solvent is present in the naphthenic (tar) fraction, it may be unnecessary to add more of such solvent to the extractor 5'.

The parainic oil and paralnic solvent are withdrawn from the top of extractor 5 and passed to suitable apparatus 6' for evaporating the solvent. Some naphthenic solvent may also be carried over and recovered, as described in connection with the paraffinic fraction from extractor 5. The oil produced will be high grade like the oil produced from the residuum, but will have a lower viscosity, and be suitable for blending with the oil from evaporator E to produce a vfull line of motor lubricants from say S. A. E. viscosity 10 to 80.

The residual fraction from the extractor 'I may be withdrawn and further treated, or disposed of as a by-product. It will contain thenaphthenic oil from both the residual charging stock and the light distillate, as will most of the naphthenic solvent and generally some parafiinic solvent, which solvents can be readily recovered by'evaperation, decantation or otherwise, for reuse in the process.

Through the employment of av naphthenic oil fraction in connection with the solvent extraction of a light stock, a number of advantages are secured. For one thing the critical solution temperature, at which the parailinic solvent solution and the naphthenic solvent solution become immiscible to such extent that a separation occurs, is raised, thus avoiding the need for cooling the mixture to a low temperature. Moreover, the character of the naphthenic fraction is such as to increase the selectivity of the solvents for type of constituents each is designed to dissolve. A superior separation results, both in respect to the purity of the products and the mechanical efllciency (speed and so forth) of the extraction. Furthermore, while distinct parafnic or lubricating oils are produced well adapted for blending, the entire naphthenic oil and tar fractions are recovered as a unit. Furthermore, savings in apparatus may be effected due to the ability to obtain a highly efficient extraction of both the light oil and the residual oil under conditions best suited to the treatment of each.

Merely by way of example, one may take a typical Appalachian crude and distill oif the gasoline, kerosene and gas oil fractions, after which a lubricating oil fraction may be distilled olf, preferably under vacuum, until an end point temperl ature, commonly considered satisfactory in reto 4separate the residuum into a lubricating oil fraction and a naphtheni'c fraction in `accordance with the' foregoing orthe disclosure of the earlier of the copending applications referred to.

' The extent -to which the refining of each fraction is carried will necessarily vary with the character of the crude charging stock, the conditions o! the'distillatlon, andthe desired purity or viscosity characteristics of the lubricating oil. However, if a 100. V. I. oil, or better, is required then the extraction may be continued or repeated until such oil is produced. When the solvents are counterowed so that the naphthenic layer is purified of constituents desirable in a paramnic layer, and the paramnlc layer is puried of constituents not desired in that layer but which belong in the naphthenic layer, then there is produced a naphthenic layer having excellent characteristics for present purposes, i. e. for aiding in the extraction of alight distillate. The proportions of naphthenic layer to distillate may vary scribed in connection with the treatment of a lubricating oil distillate, it may be used for treating other oil fractions, where it mayprove advantageous.

Turning to Fig. 2, there will now be described a somewhat more detailed process in accordance with the foregoing principles and including additional, relatively specific features.

A crude oil, such as a Mid-Continent stock, Appalachian crude, or other mineral oil, may be first distilled in suitable apparatus I 0, to take the gasoline, kerosene and gas oil overhead. These portions of the charging stock may be collected and refined in any convenient manner. The balance of the stock may then be further distilled to remove a light oil distillate and then a separate, intermediate oil. distillate, which is .relatively heavy as comparedto the light oil distillate but nevertheless taken overhead belowan end-point temperature at which undesired decomposition of the residual oil would take place. For instance, for a Mid-Continent or California high asphalt crude, this end-point temperature may advantageously be maintained below about 600 F.. more or less, depending on the particular oil distilled. The light and intermediate oils thus or otherwise produced arecollected for treatment as hereinafter described.

The residual oil from apparatus Il) is preferably solvent-extracted in extractor l I in the man.- ner described in connection with the initial treatment of residual oil with reference to Fig. l, and the high-grade parafiinic oil (which may have a viscosity index of 100 or more) is then treated in evaporator I6 to remove the solvents from it. It may be dewaxed, iiltered, clay treated or acid treated, if desired, at any convenient point in the process. The naphthenic or tarry fraction may then be passed to an extractor I2, where it may be extracted with solvent tor parainic oil to produce a second-grade oil (which may have a viscosity index below 10D but suiiiciently high for having different viscosities.

tractor AII may be by-passed by closing valve I3 and opening valve I I.

The residual oil from either the extractor II or extractor I2. as the case may be, is introduced into an extractor I I', into which the intermediate oil distillate is also admitted, and the extraction is eected preferably in the manner previously described by means of one or both of the solvents in extractor I 2', or be by-passed by proper operation of valve I l' and I4', to extractor' II, where the light oil distillate is solvent-treated in the presence of the naphthenic .or tarry fractions from previous operations A high-grade lubricating oil fraction is drawn oli from the top of extractor II" and theV solvent is removed from this fraction in-evaporator I8". The resulting fraction may be treated to further purify or improve it as mentioned in connection with the previously described high-grade oil fractions. By operating valves I3" and I4", as desired, the naphthenic or asphaltic fraction from extractor II" may be treated or not in extractor I2"' to produce a second-grade oil.

The several high-grade oil fractionsV may then otherwise improve their properties, and be b'lendv ed, if desired, in suitable apparatus (not indicated en theow sheet).

From the bottom of extractor II or I2, as the case may be, there are Withdrawn the total tars or naphthenic oils from the various extractions. The entire naphthenic solvent containedin this fraction may be recovered by evaperation vor by settling and decantation, or both,

in suitable apparatus (not indicated on the-flow sheet).

It will thus be understood that there is provided a simple andconvenient process for-producing a series of high-grade lubricating oils At the saine time, the present process provides for extracting a light oil in the presence of a naphthenic or tar fraction, which results in a superior extraction of the light oil and permits the extraction to be carried out at a higher temperature than would otherwise be feasible. That is to say, the solvent extraction must be carried out at a temperature lat which the solutions tend to separate eiliciently,

so that the parainic fraction may be drawn oli from the nap'hthenic fraction. When given solvents are employed, the critical temperature at which the layers become immiscible, or miscible to but 'a limited extent, is found to be higher where an asphaltic oil is present than Where only a light oil is present. The need for refrigeration or cooling apparatus is thus avoided, and where the solvents employed are propane and cresylic acid, for example, the process may be conducted at around 75 F.

Moreover, a high yield of lubricating oil is produced, fsince any lubricating oil not extracted down into extractor Il and again treated with paraflinic solvent. So, in extractor II" a further washing is carried out to recover additional parailnic oil. y

In addition, provision is made for recovering oils of lower viscosity index than the high-grade oils, if desired, and much flexibility is permitted.

The tars or asphaltlc and naphthenic oils are all recovered as a unit and the recovery of naphthenic solvent from them may be veected in a single operation. Thus-the apparatus required is minimized, while at the same time provision is made for the separate production of lubricating oils of various viscosities. The process is particularly advantageous in connection with plants where apparatus is already in use for distilling crude oils, where a, further saving in apparatus results. A

Inshort, a' high yield of superior lubricating oils of varying viscosities may be produced in -a simple and efllcient manner.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, oi excluding any equivalents of the features shown and described, or portions thereof, but it is recognized that various modications are possible within the scope of the invention claimed.

What is claimed is:

1. In a process for extracting a mineral oil by means of solvents, the steps comprising distilling a crude charging stock to produce a light oil distillate, extracting the residual oil from the stock by means of parailinic and naphthenic solvents which are miscible to only a limited extent, to produce a para'inic layer and a naphthenic layer, separating the layers, adding at least a portion of the naphthenic layer'to the distillate, and separating the distillate into relatively paraiiinic and naphthenic fractions by means of a paraiiinic solvent.

2. In a process for extracting a mineral oil by means of solvents, the steps comprising distilling a crude charging stock to produce a light oil distillate, extracting the residual oil from the stock by means of paraiiinic and naphthenic solvents, which are miscible to only a limited extent, to produce a parafilnic layer and a naphthenic layer, separating the layers, adding the entire naphthenic layer to the distillate, and separating the distillate into relatively paraillnic and naphthenic fractions by means of a parailnic solvent.

3. In a process for extracting a mineral oil by means of solvents, the steps comprising distilling a crude chargingstock to produce a light oil 'distillate, extracting the residual oil from the stock by means of parailnic and naphthenic solvents,

which are miscible to only a limited extent, to

produce a parafiinic layer and a naphthenic layer,

separating the layers, adding the entire naphthenic layer to the distillate, and separating the `distillate into relatively paraiiinic and naphthenic fractions by means of a parailinic solvent oil from the naphthenic' layer by means of a parailinlc solvent, adding the remainder of the naphthenic layer to the distillate, and separating the distillate into paramnlc and naphthenic fract ons.

5. In a process for extracting a mineral oil by means of solvents, the steps comprising distilling a crude charging stock to produce a light oil distillate, extracting the residual oil from the stock by means of paramnic and naphthenic solvents, which are miscible to only a limited extent, to produce a paraiilnic layer and a naphthenic layer, separating the layers, extracting a paraiilnic oil from the naphthenic layer by means of a paraiiinic solvent, adding the remainder of the naphthenic layer to the distillate, and separating the distillate, into paraillnic and naphthenic fractions by means of a paraiilnic` solvent.

6. In a process for extracting a mineral oil-by means of solvents, the steps comprising distilling a crude charging stock to produce alight oil distillate, extracting the residual oil from the stock by means ofcounteriowing paralnic and naphthenic solvents, which are miscible to only a limited extent, to produce a parafdnic layer and a naphthenic layer, separating the layers, adding at least a portion'of the naphthenic layer to the distillate, and separating the distillate into relatively lparafllnic and naphthenic fractions by means of counterowing solvents which are miscible to only a limited extent.

7. In a process for rening mineral oils, separating a crude into a plurality of portions by distillation, extracting the resulting residue by means of paraflinic and naphthenic solvents, adding at least a portion of the naphthenic fraction thus produced 4to'one of said distilled portions, extracting the resulting mixture with paraiiinic and naphthenic solvents, and extracting another of said distilled portions with a solvent in the presence 'of at least a portion of the naphthenic oil resulting from the extraction of the first-named distillate portion,

8. Methodof refining a mineral oil which comprises extracting at least a portion of said oil with parailinic and naphthenic solvents to produce a high-grade paraflinc oil and a relatively naphthenic oil,jtreating said naphthenic oil with paraillnic solvent, removing the parafll'nic solvent and dissolved constituents from the said naphthenic oil, mixing'the balance of said naphthenic oil with a light mineral oil distillate, extracting the mixture thus produced with solvent to produce a high-grade parailinic oil, and extracting the balance of the mixture to produce another parafdnic oil fraction.

9. Method of rening a mineral oil which comprises distilling'said oil to produce a light oil, distilling said mineral `oil to produce an intermediate distillate, treating the light oil with parailinic and naphthenic solvents, removing a naphthenic fraction from the light oil and introducing said fraction to the intermediate disiillate in-the presence oi' parafnic solvent, removing a naphthenic fraction from said intermediate distillate, conducting said last named naphthenic fraction to the residue of the mineral oil in the presence of a parafnic solvent, and withdrawing a naphthenic fraction from said residue. whereby the naphthenic portions of said light oil, said intermediate distillate and said residue are recovered as a unit.

10. In alprocess for reilning a crude mineral oil by means of solvents, the steps comprising distilling a crude charging stock .to produce a 2,041,808 `relatively light oil distillate, extracting the residual oil from said stock by means of a naphthenic solvent to produce a railinatephase and an extract phase, and extracting the aforementioned distillate with at least a portion of said extract phase containing naphthenic constituents oi' the residue and naphthenic solvent.

11. In a process for reilning a crude mineral oil by means-of solvents, vthe steps comprising 10 distilling a crude charging stock to produce a relatively light oil distillate, extracting the residual oil from said stock by means of parainic and naphthenic solvents which are miscibie to only a limited extent to produce a rafnate phase and an extract phase,v and extracting the aforementioned distillate with at least a portion of said extract phase 'containing naphthenic con-l stltuents of the residue and naphthenic solvent.

MALCOLM H. TUTI'LE. 

